The Quest for Stable Potassium‐Ion Battery Chemistry

Abstract

Potassium-ion batteries (KIBs) have attracted wide interests for energy storage because of the abundance of the electrode materials involved; however, their electrochemical performances are far behind what can be achieved from lithium-ion batteries (LIBs) or sodium-ion batteries (SIBs). This paper identifies key promising electrode and electrolyte materials for potassium-ion batteries, investigates the coupled electrochemical reactions in the cell, and demonstrates that the compatibility between different materials plays the most important role. K₂Mn[Fe(CN)₆] cathode can deliver a high capacity of ∼125 mAh g^–1 and exceptional cycling stability over 61,000 cycles (∼9 months) if the side reactions from the anode can be prevented. Graphite is a good anode material but is subjected to degradation in traditional carbonate electrolytes. New concentrated electrolytes are developed and evaluated. A stable KIB system is demonstrated by coupling a stable K₂Mn[Fe(CN)₆] cathode, a pre-potassiated graphite anode with a concentrated electrolyte to achieve a high energy density of ∼260 Wh kg^–1 (based on the active mass of cathode and anode) and good cycling of over 1000 cycles. This article is protected by copyright. All rights reserved